Implement common subexpression elimination

Signed-off-by: Lucas Steuernagel <[email protected]>

examples/test.sol

@@ -0,0 +1,42 @@
+contract foo {
+
+     struct stTest {
+        int a;
+        uint b;
+    }
+
+    function test6(int a, int b) public view returns (int ret) {
+        stTest instance = stTest(2, 3);
+        int x = a + b + instance.a;
+        if(x  + int(instance.b) < 0) {
+            // Erro aqui?
+            uint p = uint(a+b+instance.a);
+            bool e = p > 50;
+        }
+
+        int8 trunc = int8(x);
+        bool e2 = trunc > 2;
+        int8 trunc2 = 8 + int8(x);
+        bool e3 = trunc2 < trunc;
+        bool e4 = e2 || e3;
+
+        if (trunc2 < trunc && trunc > 2) {
+            int p2 = a+b;
+            int p3 = p2 - x + a + b;
+            int p4 = p2-x;
+            int p5 = p3 + a*b+45;
+
+            if (p5 !=0) {
+                uint16 t1 = uint16(p3 + a*b +45);
+                uint32 t2 = uint32(a*b);
+                bool e5 = t2 < t1;
+            }
+
+            ret = p3 + a*b + 45;
+        }
+
+        ret = a*b;
+    }
+
+
+}

src/bin/solang.rs

@@ -156,6 +156,12 @@ fn main() {
                 .long("math-overflow")
                 .display_order(5),
         )
+        .arg(
+            Arg::with_name("COMMONEXPRESSIONELIMINATION")
+                .help("Disable common subexpression elimination")
+                .long("common-elimination")
+                .display_order(6),
+        )
         .arg(
             Arg::with_name("LANGUAGESERVER")
                 .help("Start language server on stdin/stdout")
@@ -307,6 +313,7 @@ fn main() {
             strength_reduce: !matches.is_present("STRENGTHREDUCE"),
             constant_folding: !matches.is_present("CONSTANTFOLDING"),
             vector_to_slice: !matches.is_present("VECTORTOSLICE"),
+            common_subexpression_elimination: !matches.is_present("COMMONEXPRESSIONELIMINATION"),
             math_overflow_check,
             opt_level,
         };